The structure of the lac promoter will be further analyzed by (1) determining the sequence changes caused by a variety of lac promoter mutations, (2) establishing a system for in vitro directed mutagenesis of the lac promoter restriction fragment in order to generate more promoter mutations, and (3) analyzing the effect of promoter mutations on RNA polymerase binding and transcription initiation. The structure of other promoter regions will be studied such as the thr operon promoter and the promoters associated with the tet and kan transposition elements. BIBLIOGRAPHIC REFERENCES: Dickson, R. C., Abelson, J., Johnson, P., Reznikoff, W. S. and Barnes, W. M. (1977). Nucleotide sequence changes produced by mutations in the lac promoter of Escherichia coli. J. Mol. Biol. 111: 65-77. Reznikoff, W. S. and Abelson, J. (1977). The lac promoter. "Molecular Aspects of Operon Control" (eds. Miller and Reznikoff) Cold Spring Harbor Laboratory. In press.